352 EFFECTS OF SNAKE VENOMS ON DOMESTIC ANIMALS. 



tion of 50 mgm., and thus to obtain some idea of its antivenomous 

 properties. 



The sernni is considered to be ready for isstie when i c.c. 

 mixed with i mgm. of venom produces no symptoms on being 

 injected into a rabbit; and when 2 c.c. of serum protects a rabbit 

 of 2 kilos, against an injection of i mgm. of venom two hours 

 later. 



This is a rough-and-ready method, and gives no idea of the 

 actual valency of the serum, so, in order to obtain definite infor- 

 mation on this point, it is necessary to carry out a series of tests 

 on rabbits to ascertain the amoiuit of senmi required to protect 

 against a minimal lethal dose per kilo, of venom to be used for 

 test purposes. (Jwing to the wide variations in toxicity which 

 occur in venoms collected from different snakes, it is necessary 

 to ascertain ])reviously the minimal lethal dose ])er kilo, of rabbit 

 by experiment, otherwise the results of the serum test cannot 

 be taken as absolutely accttrate. As a guide I give herewith the 

 minimal lethal dose of venoms from the more common poisonous 

 Sotith African snakes. The figm-es have been com]:)iled from a 

 series of experiments carried out on rabbits at Pietermaritzburg 

 Laboratory : — 



Minimal Lethal Dose per Kilo. 



Snake. Animal. Intravenous. Subctitaneous. 



mgm. 



Bitis arlclans Rabbit 0.5 .... 



Dendraspis ., 0.225 .... 



Naja iilgrlcollis . ... 0.9 .... 



N'aja fia7'a 1.5 .... 



Caitsiis rhoifibealiis . . ., 4 .... 



Scpedon hccuiorlwlcs 0.21 .... 



In the intravenous niethcxl of antivenomous serum ])roduc- 

 tion, serum can be produced of more than three times the activity 

 necessary to fulfil these conditions. This is specially the case 

 in. \'iperine antivenene. 



A polyvalent serum has been prepared at the Pietermaritz- 

 burg Laboratory against mamba, puff-adder, and cobra venoms, 

 and the results in the case of the two latter snakes' venom have 

 been extremely satisfactory. No opporttmity, so far as I am 

 aware, has ever occurred for testing its efficacy against mamba 

 venom, and as applications for serum containing mamba are so 

 rare, this venom has now been omitted from antivenene work. 

 The preparation of a polyvalent serum requires more time, and 

 its production is attended with more risk of death of the animal 

 being hy])erimmunised than in the case of serum ])rei)ared 

 against one species of snake. It is also difficult to obtain maxi- 

 mum activity of all its components, and it is often found on test 

 that one or other is deficient. I am therefore of the opinion that 

 a much more constant and efiicacious polyvalent serum could be 

 prepared by mixing monovalent sera of maximum valency. 



This, so far as I am aware, has not yet been tried, but I see 

 no reason why the results should not be successful. The method 



